What is the meaning of single and double color LED screen?
Author:Zhong Keyu Time:2021-06-10 16:53 Browse(197)
The luminous color and luminous efficiency of LED are related to the material and technology of making LED. At present, red, green and blue are widely used. Due to the low working voltage of LED (only 1.5-3V), active lighting and certain brightness, brightness can be adjusted by voltage (or current), shock resistance, vibration resistance and long service life (100000 hours), there is no other display mode that can match LED display mode in large display equipment.
At present, red, green and blue LEDs are widely used.

What is the meaning of single and double color LED screen?

due to their low working voltage (only 1.5-3V), they can emit light actively and have a certain brightness, which can be adjusted by voltage (or current), and they are shock resistant, vibration resistant and have a long service life (100000 hours), At present, there is no other display mode that can match the LED display mode.
there is no other display mode that can match the LED display modeThe red and green LED together as a pixel production screen is called two-color screen or color screen; The display screen with red, green and blue LED tubes together as a pixel is called three color screen or full color screen.
the pixel size of indoor LED screen is generally 2-10 mm.
several kinds of LED chips that can produce different primary colors are often packaged into one. The pixel size of outdoor LED screen is mostly 12-26 mm, and each pixel is composed of several monochrome LEDs. The common finished product is called pixel tube, Two color pixel tube is generally composed of 3 red and 2 green, and three color pixel tube is composed of 2 red, 1 green and 1 blueNo matter using led to make monochrome, bicolor or tricolor screen.
to display an image, the brightness of each LED that constitutes a pixel must be adjustable, and the fine degree of adjustment is the gray level of the display screen.
the higher the gray level is.
the more delicate the image is, the richer the color is, The corresponding display control system is more complex.
generally, the color transition of 256 level gray image is very soft, while the color transition boundary of 16 level gray image is very obvious.
therefore.
Color LED screen is required to be 256 level gray.
this paper introduces the design of color LED screen2、 Methods to control LED brightness:There are two ways to control the brightness of LED.
there are two ways to control the brightness of LEDOne is to change the current flowing through the LED.
generally, the continuous working current of LED is about 20 mA. Except for the saturation of red LED, the brightness of other LEDs is basically proportional to the current flowing through; Another method is to use the visual inertia of human eyes, and use the pulse width modulation method to achieve gray control, that is to change the light pulse width (i.e. duty cycle) periodically, as long as the cycle of repeated lighting is short enough (i.e. the refresh frequency is high enough), The human eye can't feel the light-emitting pixels shaking.
because PWM is more suitable for digital control.
today, microcomputer is widely used to provide LED display content, almost all LED screens use PWM to control the gray level.
in this paper, the author analyzes the application of PWM in LED displayThe control system of LED is usually composed of main control box, scanning board and display control device.
the main control box obtains the brightness data of a screen pixel from the display card of the computer.
then it is redistributed to several scanning boards, each scanning board is responsible for controlling several rows (columns) on the LED screen, At present, there are two ways of serial transmission of display control signal: one is to control the gray level of each pixel on the scanning board centrally.
the scanning board decomposes the brightness value of each pixel from the control box (i.e. pulse width modulation), and then turns on the signal of each LED in the form of pulse (light up to 1, light up to 1, light up to 1, light up to 1, light up to 1, light up to 1, light up to 1, light up to 1, light up to 1, light up to 1, light up to 1, light up to 1, light up to 1, light up to 1, In this way, less devices are used.
but the amount of serial transmission data is large, because in a repeated lighting cycle, each pixel needs 16 pulses at 16 gray levels and 256 pulses at 256 gray levels, Generally, the LED screen can only achieve 16 gray levelsAnother method is that the serial transmission content of the scanning board is not the switch signal of each LED, but an 8-bit binary brightness value.
each LED has its own pulse width modulator to control the lighting time.
in this way.
in a repeated lighting cycle, each pixel only needs 4 pulses in 16 level gray, and only needs 8 pulses in 256 level gray, The serial transmission frequency is greatly reduced.
with this method of decentralized control of LED gray level, 256 level gray level control can be easily realized.
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can be realized
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